The effects of prenatal alcohol exposure on the developing human brain will be examined in a cohort of low birthweight infants assembled to study the causes and consequences of neonatal brain hemorrhage. In this prospective, population-based study, 763 mothers of infants < 2000g were interviewed in person, immediately after delivery, about alcohol consumption patterns throughout the pregnancy, as well as about a range of other prenatal exposures and behaviors. Their infants received cranial ultrasound scans according to a prospective protocol at three post-natal intervals, and head circumference measurements at birth, at each ultrasound examination, and weekly prior to hospital discharge. Ultrasonographic information was obtained on the presence or absence of germinal matrix and intraventricular hemorrhage, white matter and cortical necrosis, and ventricular enlargement. Ultrasound scans were routinely read by two, and if needed, three independent interpreters, without knowledge of the clinical state of the infant. The medical records of both mothers and infants were abstracted in detail. 82% of the surviving infants were examined for neurological, cognitive, behavioral and sensory abnormalities at age two years. This data will be used to examine the relationship between prenatal alcohol exposure and CNS development among low birthweight infants. The analyses will test whether alcohol exposure in utero, increases the risk of ultrasonographically defined germinal matrix/intraventricular hemorrhage or brain parenchymal necrosis, alters the clinical outcomes following these lesions, or impacts on head circumference and/or development at age two years in non-brain injured low birthweight infants. This data set is unique both for its size, and for the detailed information available on brain injury and development, and presents an opportunity to assess, for the first time, prenatal alcohol use in relation to childhood cognitive development, taking account of changes in the size and state of the brain in the newborn period.